Friction gear transmission systems or components – Friction gear includes idler engaging facing concave surfaces – Toroidal
Reexamination Certificate
2000-02-11
2002-02-05
Herrmann, Allan D. (Department: 3682)
Friction gear transmission systems or components
Friction gear includes idler engaging facing concave surfaces
Toroidal
C029S465000, C029S509000, C072S377000
Reexamination Certificate
active
06344013
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a toroidal-type continuously variable transmission for an automobile and a method for manufacturing a trunnion for use in the present toroidal-type continuously variable transmission.
2. Description of the Related Art
Conventionally, a toroidal-type continuously variable transmission is known, for example, in Japanese Utility Model Unexamined Publication No. 62-71465 of Showa. That is, as shown in
FIGS. 4 and 5
, on a shaft
1
, there are rotatably supported an input disk
2
and an output disk
3
through needle shafts
4
. On the back surface side of the input disk
2
, a cam plate
5
is spline engaged with the shaft
1
, a plurality of rollers
6
are interposed between the cam plate
5
and input disk
2
, and there is disposed a pressure mechanism
7
of a loading cam type which is used to press the input disk
2
toward the output disk
3
side. The output disk
3
is engaged with an output gear
9
through a key
8
, so that the output disk
3
and output gear
9
are able to rotate synchronously with each other.
Between the input disk
2
and output disk
3
, there is interposed a trunnion
11
which is able to swing about a pivot shaft portion
10
and, in the central portion of the trunnion
11
, there is disposed a displacement shaft
12
. And, on the displacement shaft
12
, there is rotatably supported a power roller
13
. This power roller
13
includes a traction portion in contact with the input disk
2
and output disk
3
, while the power roller
13
is rollably contacted in such a manner that it can incline on and between the input disk
2
and output disk
3
.
Also, between the trunnion
11
and power roller
13
, there is disposed a power roller bearing
14
. This power roller bearing
14
, while carrying a load applied to the power roller
13
in its thrust direction, allows the rotation of the power roller
13
. In the power roller bearing
14
, a plurality of balls
15
are held by an annular retainer
17
which is interposed between an annular outer race
16
disposed on the trunnion
11
side and the power roller
13
serving as a rotary part.
Further, the trunnion
11
comprises a main body plane portion
18
and the above-mentioned pivot shaft portions
10
respectively formed integrally with the two end portions of the main body plane portion
18
; and, in the main body plane portion
18
, there is formed a circular hole
19
. In the circular hole
19
, there is disposed a needle bearing
20
, so that the displacement shaft
12
is supported in a freely rotatable manner. Also, the two pivot shaft portions
10
respectively disposed on the two end sides of the trunnion
11
are respectively supported on a support plate
21
in such a manner that they can be swung with respect to the support plate
21
, whereby the inclination angle of the displacement shaft
12
can be freely adjusted by the swing motion of the trunnion
11
.
Further, to one end portion of each of the trunnions
11
, there is connected a drive rod
22
; on the outer peripheral surface of the middle portion of the drive rod
22
, there is disposed a drive piston
23
; and, a drive cylinder
24
is inserted into the drive piston
23
.
According to the above-structured toroidal-type continuously variable transmission, rotation transmitted to the cam plate
5
of the pressure device
7
from a drive source such as an engine is transmitted through the rollers
6
to the input disk
2
. The rotation of the input disk
2
is transmitted through the power roller
13
to the output disk
3
, while the rotation of the output disk
3
is taken out from the output gear
9
.
To change a rotation speed ratio between an input side and an output side, a pair of drive pistons
23
may be shifted in the mutually opposite directions. With such shifts of the drive pistons
23
, the trunnions
11
are also respectively shifted in the mutually opposite directions. This changes the direction of the tangential-direction force that acts on the contact portions between the peripheral surfaces
13
a
of the power rollers
13
and the inner peripheral surfaces
2
a
,
3
a
of the input and output disks
2
,
3
; and, with such change in the direction of this force, the trunnions
11
are respectively swung in the mutually opposite directions about their associated pivot shaft portions
10
pivotally supported by the support plate
21
.
By the way, as shown in
FIG. 6
, the conventional trunnion
11
is worked by cutting a blank material consisting of a round rod. And, in case the trunnion
11
is experimentally assembled into a toroidal-type continuously variable transmission and a large torque is repeatedly input to the toroidal-type continuously variable transmission, an excessive load is input to the power roller
13
, with the result that an excessive load is repeatedly applied to the trunnion
11
backing up the power roller
13
.
On the other hand, since the toroidal-type continuously variable transmission is carried on board a car, the trunnion
11
must also have the necessary and minimum dimension. Therefore, due to the large load repeatedly applied, the center portion of the main body plane portion
18
of the trunnion
11
, while supporting the two ends of the pivot shaft portions
10
, is bent repeatedly. That is, when the displacement is large, there is applied a force of 4t or more when the maximum load of the engine of the car is applied to the trunnion
11
in the maximum deceleration, so that there is applied to the trunnion
11
such a large bending stress as shown by a broken line in FIG.
6
.
As a result of this, the connecting portions A between the pivot shaft portions
10
and main body plane portion
18
, in which the stress becomes the highest, is pulled and returned back to their original conditions repeatedly; that is, the bending stress is applied collectively to the connecting portions A, so that the connecting portions A are finally cracked and broken.
The reason for this is believed that the conventional trunnion
11
is formed by cutting a round rod and thus, as shown in
FIG. 7
, metal flows
11
a
at the high-stress portions of the trunnion
11
are cut off. Therefore, the present inventors have conducted another test in which a trunnion
11
is formed by cutting a flat plate instead of the round rod. However, in this test as well, the results are similar to those in the former test.
SUMMARY OF THE INVENTION
The present invention aims at eliminating the drawbacks found in the conventional toroidal-type continuously variable transmission. Accordingly, it is an object of the invention to provide a toroidal-type continuously variable transmission which can prevent a trunnion against damage even when an excessive load is repeatedly applied thereto to thereby be able to enhance the durability of the trunnion and thus the toroidal-type continuously variable transmission.
In attaining the above object, according to the invention, there is provided a toroidal-type continuously variable transmission comprising: an input disk; an output disk disposed coaxially with the input disk; a trunnion capable of swinging about its pivot shaft portion situated at a torsional relation with respect to the respective center axes of the input and output disks; and a power roller supported on the trunnion and inclinably rollable on and between the input and output disks, wherein the trunnion comprises a main body plane portion for holding a displacement shaft supporting the power roller rotatably and a pair of pivot shaft portions respectively formed in the two end portions of the main body plane portion integrally therewith, while two connecting portions respectively between the main body plane portion and the pair of pivot shaft portions are respectively formed so as to include continuous metal flows. Here, “torsional relation” of the pivot shaft portion means a physical relation that the pivot shaft portion is disposed at position along an imaginary plane that is perpendicular to an imaginary line connecting th
Herrmann Allan D.
NSK Ltd.
Sughrue & Mion, PLLC
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